Air Asia

I found a great deal on AirAsia, but I can't seem to get the deal when I try to book it.   I know that they add on taxes and charge for assigned seats and all that, but the price of the flight (before the taxes, ect) is almost 100,000 won more than advertised.   Also, I tried calling their customer service line but never got through. 

Has anyone else experienced this and can enlighten me as to how to get the 'deal'? 

Is there an AirAsia office in Busan that I could visit?